Hearing Pitch or Sound Frequencies

by Ron Kurtus (7 March 2001)

Humans and animals can sense a wide range of sound frequencies, pitches or tones. The range of frequencies determines the person's or animal's perception of the world, as well as its ability to communicate.

Questions you may have include:

What are sound frequencies?

What is the range of frequencies for the different animals?

How does this affect a person's perception of the world?

This lesson will answer those questions.

Frequencies

The frequency of a sound is also known as its pitch. The higher the frequency, the higher the pitch and the shorter its wavelength. There is a range of frequencies that humans and animals can hear or detect. This is also true for any detectors of sound, such as microphones.

Frequency is measured in Hertzwhich means cycles per second. The abbreviation for Hertz is Hz.

Range of frequencies

There is an upper and lower limit of the frequencies that each animal can hear. The following chart shows a comparison of the range of frequencies or pitches that humans and various animals can hear. Note that a frog and a mouse hear almost a completely different range of sounds.

Range of hearing in Hertz

Humans have limitations

A normal human can hear between 20 Hz and 20,000 Hz. That is quite a range. 20 Hz is a very low pitch sound or very deep tones. 20,000 Hz is a high pitch sound. Besides hearing low frequencies, you can often feel them. An example of that is when you can feel the bass from a loudspeaker.

When humans get older, they have trouble hearing the high pitched sounds and their detection range diminishes. For example, I knew an old man who was losing his ability to hear the higher pitched sounds. He could hear my voice fine, but he had trouble hearing his wife, because her voice was at a higher pitch. She often got angry at him, because she thought he was just ignoring her.

Dogs can hear high notes

Dogs and some other animals can hear sounds at higher frequencies than 20,000 Hz. That is why people cant hear a special dog whistle, while the dog will react to it. Being able to hear the higher frequencies may be useful in hunting for the animal. Cats can hear higher frequencies also, but most are too independent to respond to such a whistle.

Elephants can hear low notes

Elephants can hear frequencies much lower than the range of humans. Some researchers who were studying elephants in Africa discovered this. The story goes that a herd of elephants they were observing suddenly perked up their ear and ran off in a direction, as if they heard someone calling them. The researchers said they didn't hear anything, but some said they felt something strange in their bodies, just before the elephants ran off.

After studying this situation, they found that elephants could make a very low frequency sound that humans cant hear. Elephants are able to hear this sound coming from up to 5 miles away. It is amazing the distances from while they can communicate with each other.

Perception of world

What you hear can affect how you perceive the world around you. The whine of the vacuum cleaner may not bother you, but it can cause your dog to run and hide, because of the painful high-pitched sound that you may not be able to hear.

Cats perceive a world where there are high-frequency squeaks of mice hiding in the pantry, while elephants perceive a world of low rumbles of far-away friends. Meanwhile, we perceive a world somewhere in between.

Summary

The pitch of a sound is determined by its frequency, which is usually measured in Hertz. Animals and humans can hear sounds in limited range of frequencies. Some animals can hear sounds that humans cant. The range of sound you can hear determines your perception of the world.